1. Field of the Invention.
This invention relates to a Plastic Ball Grid Array ("PBGA") stiffener package and method of manufacturing same.
2. Discussion of Related Technology.
Referring to FIG. 1, previously, in the manufacturing of PBGA packages 10, a thixotropic damming compound, formed as a damming ring 12, was used to surround an integrated circuit die 16 attached to an individual PBGA member 22. Bond wires 18 were then attached to the die 16 to form electrical interconnects with signal tracks 42 (FIG. 4a), which in turn connected to solder ball pads 52 (FIG. 4b) on the solder ball attach surface 50 on the underside of the PBGA member 22. Solder ball 20 were then attached to selected pads 52. Inside the perimeter of damming ring 12, a low stress epoxy was then applied to form an encapsulate 14 over the die 16 and the interconnect bold wires 18.
The resulting prior art PBGA package 10 shown in FIG. 1, typically had a coplanarity of, at best, about 18 mil (0.018 inches). This degree of coplanarity has become increasingly unacceptable for many customers who find that PBGA packages manufactured in this fashion contain shorting at the solder ball connections due to package warpage. Alternate existing methods of construction, which include overmoled PBGA packages and glob top PBGA packages, have distinct disadvantages as well. Overmoled PBGA packages require lengthy cycle times and relatively high associated tooling costs. Glob top PBGA packages frequently fail the reduced coplanarity requirement of customers by allowing too much package warpage causing electrical disconnects at the solder joints.
Many customers now demand coplanarity for a PBGA package to be less than 8 mils. Thus, the need has arisen for a PBGA package, and method of manufacturing same, which results in a coplanarity of less than 8 mil to prevent inadvertent electrical disconnects at the solder joints through ensured PBGA package coplanarity, rigidity and board mountability.